I have a 2004 Mazda 6 with an automatic transmission. Lately when I turn off the engine, it sounds like it's still running and sometimes sounds like it's revving up. Sometimes it does this for as long as thirty seconds. Has anyone else experienced this or have any idea what the problem might be? I'm going to bring it in to the dealership as soon as I have a break at work.

 

it is possibly your a/c compressor fan cooling the compressor down. do you run the air conditioning and then turn the car off? especially if you run the a/c for a long period of time, the compressor fan will stay on to cool the compressor down after the car has been turned off...completely normal.

 

Yes, I almost always have the a/c on, but even if I just have the car on for a minute to move it out of the driveway (and don't have the a/c on) it still makes the noise for a few seconds after I turn the engine off. I guess I was concerned because it didn't do this for the first two years that I had the car. What would cause it to start doing it now? Should I be doing something differently regarding the a/c?

 

It sounds like dieseling to me.

In technical terms, your fuel is igniting itself without any spark (ignition off). This is caused by a combination of warm engine, high compression, and low octane. You have no control over warm engine or high compression, those are by design

Try a tank or two of higher octane gasoline, or perhaps just switch to a different brand of gasoline.

Mark in MA

 

Does your 6 have a V6 engine or 4 cylinder?
After you turn the car off, open the hood and see if the cooling fans are still running and speed varies somtimes. 2003-2004 6 cars with V6 engine had faulty fan control modules that should have all been replaced by Special Service Program #60. Even ones outside of this range have had some problems. Symptoms are usually that the fan runs after engine shut off, all of the time, or speed varies/fluctuates up and down excessively. Pic below is of the fan control module on the V6 engine 6's. It is the square box that is smooth black towards rear and lumpy aluminum towards front. If you do open the hood with car off but fan still running or even when engine is running and fan speed is fluctuating all over the place then give that box a little whack with something hard like the handle of a screwdriver. If fan speed suddenly changes or shuts off altogether then the module is faulty.

[IMG]local://upfiles/1377/DEB29FAE6DA845B2BB7C6E12B9BF0494.jpg[/IMG]

 

BabyH,

Is this fan issue common in the 06' model?

Mine seems to do it, sometimes 10 secs, sometimes up to 45 sec after I turn off
and get out..
I figured it was the fan cooling something off, but the irregular speed is what prompts my
interest in a solution.

 

My 05 had the problem; sadly my dealer sucks and always fobbed me off with 'normal condition' - finally thanks to a post on here i got it fixed.

 

Is the ENGINE running, or is the FAN running after the car is turned off?

If it's the FAN it could just be the module issue which is a recall or TSB.

If the ENGINE is running, you are dieseling, where the engine continues running due to an uncontrolled ignition source, i.e. hot exhaust valve, spark plug ground, or carbon deposit on head/cylinder wall. This is more common in carbureted cars than fuel injection cars due to the mechanical fuel pump that keeps pulling gas from the tank, it would end pretty quickly in a fuel injected car, cause it'd stop when there is no more fuel in the lines (I don't think the fuel pump is a flow-through).

 

When this occurs, quickly unlatch the hood, hop out, open the hood, and check to see if it's actually the engine that's running. It should be obvious by checking the passenger side of the engine compartment, where the serpentine belt is.

Is it not HIGHLY unusual for a modern car ('00 or newer) to diesel? For that matter, a '90's car? I thought that technology had all but eradicated dieseling in modern cars. Especially considering that my '04 Mazda6 V6 calls for plain old 87 Octane gas. How very strange.

David